Wind is a clean source of renewable energy that produces no air or water pollution.
风是一种清洁的可再生能源，不产生空气和水污染。
It is a main source of air pollution in cities.
它是城市主要的空气污染源。
Cars, being the greatest source of air pollution, can be left at home this weekend.
汽车是空气的主要污染源，这个周末可以别开车了。
Uncontrolled it is a serious source of air pollution.
如果不进行控制将造成很严重的环境污染。
Uncontrolled it is a serious source of air pollution.
如果不进行控制将造成很严重的环境污染。
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